Method of constructing a refractory wall in a float glass furnace

ABSTRACT

A refractory wall is constructed by casting a first layer of refractory concrete next to the shell and while the castable is still in a castable condition, carbon bricks or blocks having an interlocking or interengaging configuration on one face are pushed into the castable to cause the castable to enter the interlocking configuration and upon setting lock the bricks to the castable layer. Carbon powder with or without a binder can be placed in the joints between the carbon blocks. Metal anchors can also be used to hold the castable layer tightly against the shell.

United States Patent [191 Brichard Mar. 26, 1974 [75] Inventor:

[73] Assignee: Glaverbel, Watermael-Bortsfort,

Belgium 22 Filed: Feb. 16, 1972 21 A i. No.: 226,703

Related U.S. Application Data [63] Continuation-impart of Ser. No.873,141, Oct. 29,

l969, Pat. NO. 3,657,399.

Edgard Brichard, Jumet, Belgium [52] U.S. Cl. 264/30, 65/182 R, 266/43,266/43, 263/46 [51] Int. Cl. F27d 1/16 ['58] Field of Search 264/30;65/182 R 56] References Cited UNITED STATES PATENTS 3,657,399 4/1972Brichard 264/30 3,575,694 4/1971 Bigliardi, Jr. et al. 65/182 R3,594,147 7/1971 Galey et al 264/30 1,452,432 4/1923 Miller 1. 52/5982,042,870 6/1936 Stafford 264/30 3,442,669 5/1969 Osterholtz.. 106/563,442,670 5/1969 Parsons 106/56 Greenler 65/182 R 3,486,878 12/19693,492,108 1/1970 Augustin et al.... 65/182 R 3,526,523 9/1970 Holden106/56 3,584,475 6/1971 Galey et a1 65/182 R 3,584,477 6/1971Hainsfurther.. 65/182 R 3,594,148 7/1971 Smith et al 1 65/182 R3,625,668 12/1971 Greenler 65/182 R 3,655,356 4/1972 Javaux 65/182 R3,669,640 6/1972 Brichard et a1. 65/182 R 3,376,681 4/1968 Demaison62/598 Primary Examiner-Robert F. White Assistant ExaminerThomas P.Pavelko Attorney, Agent, or FirmEdmund M. Jaskiewicz [57] ABSTRACT Arefractory wall is constructed by casting a first layer of refractoryconcrete next to the shell and while the castable is still in a castablecondition, carbon bricks or blocks having an interlocking orinterengaging configuration on one face are pushed into the castable tocause the castable to enter the interlocking configuration and uponsetting lock the bricks to the castable layer. Carbon powder with orwithout a binder can be placed in the joints between the carbon blocks.Metal anchors. can also be used to hold the castable layer tightlyagainst the shell.

9 Claims, 10 Drawing Figures LllllXl'I/lll/l PATENTED MARZS I974 SHEEI 50f 5 Fig.9.

Fig. 70.

METHOD OF CONSTRUCTING A REFRACTORY WALL IN A FLOAT GLASS FURNACERELATED APPLICATIONS The present application is a continuation-in-partof the copending application having Ser. No. 873,141 and filed on Oct.29, 1969 now U.S. Pat. No. 3,657,399 by the same-named applicant.

The present invention relates to float glass furnaces, moreparticularly, to a process for manufacturing a refractory body which maybe used in the construction of a furnace wall.

Furnace walls have been lined with refractory ceramics and otherrefractory materials in the form of prefabricated blocks or bricks. Notonly must the lining provide good heat insulation but must also meetother requirements based upon mechanical strength and physical behaviorpresent at the high temperatures existing within the interior of thetank during operation.

The furnace lining must also be resistant to chemicals encountered invarious industrial processes, such as by alkaline substances present inthe internal atmosphere of the furnace. By way of example, in theglassmanufacturing industry furnace tanks are employed to contain bathsof molten glass or of molten metal or metal salts. Such baths have astrong corrosive action on many refractory substances. Those refractorysubstances which have the desired heat-insulating and mechanicalproperties do not always have the required resistance to chemicalattack. Therefore, the selection of a refractory substance represents acompromise in that the properties of the substance must be balancedagainst eachother with respect to the particular application of therefractory.

lt is therefore the principal object of the present invention to providea novel and improved process for manufacturing a refractory bodyparticularly adapted for use in a float glass furnace. y

it is another object of the present invention to provide a novel andimproved refractory body for furnace walls and thelike.

It is another object of the present invention to provide a process ofmakinga refractory body from different refractory. materials so that theseveral properties of the different materials are imparted individuallyto the refractory body as a whole.

According to one aspect of the present invention a method of making arefractory body such as for a furnace wall and the like may comprise thestep of casting a refractory mass. A covering layer is then formed on atleast a portion of a surface of the refractory mass before the mass hasset. At least the layer of the surface remote from the mass has acomposition different from that of the mass. The covering layer may berich in carbon and may comprise at least one prefabricated member shapedso as to interengage with the refractory mass when the mass is set.

Other objects and advantages of thepresent invention will be apparentupon reference to the accompanying description when taken in conjunctionwith the following drawings, which are exemplary, wherein:

FIG. 1 is a vertical sectional view of a portion of a float tankinsulation incorporating a refractory body according to the presentinvention;

FIG. 2 is a transverse sectional view in enlarged scale of portions of aside and bottom wall of the float tank of FIG. 1; and

FIGS. 3-10 are transverse sectional views in enlarged scale of portionsof the tank bottom wall showing modifications of the refractory bodyaccording to the present invention.

' Proceeding next to the drawings wherein like reference symbolsindicate the same parts throughout the various views a specificembodiment and modifications of the present invention will be describedin detail.

The apparatus illustrated in F IG. 1 comprises a melting tank 1, a floattank 2 and an annealing lehr 3. The float tank comprises a bottom wallor floor 4, a crown 5, side walls 6 and end walls 7, 8 spaced from thecrown 5 by slots 9, 10. All these described components of the float tank2 are made of refractory materials. A metal wall 11 hermeticallyencloses the floor 4, side walls 6 and end walls 7, 8 of the tank whichcomprises a bath of molten material 12 which is usually molten tin butmay be molten silver or a molten metal salt.

The melting tank 1 contains a bath of molten glass 13 which is cast overa casting lip 14 between casting rollers 15, 16 which shape a glassribbon 17. The glass ribbon 17 is then conveyed by a series oftransporting rollers 18 to the slot 9 of the float tank in which it isdeposited on the bath of molten material 12 while continuing to move inthe direction indicated by the arrow X. The glass ribbon is firepolished on the bath of molten material 12 and moves toward slot 10 ofthe float tank from which it is conveyed by rollers l9 to the annealinglehr 3,

In FIG. 2 there is illustrated a portion of the bottom wall 4 andadjoining side wall 6 of the float tank 2. These walls each comprise alayer 24 of monolithic refractory concrete supported on a bottom metalwall 22 and against a side wall 23. A covering layer or lining of carbonblocks 26-30 is interengaged with the interior surface of the layer 24.Each of the carbon blocks is in the form of a rectangular parallelepipedand has a longitudinally extending dovetail groove 31 in its. bottomsurface. The carbon blocks 26-30 are exposed to a bath of moltenmaterial 33 which may be a molten salt or a molten metal such as tin. Aglass ribbon 34 floats on the bath 33 of molten material and-advanceswithin the tank in a direction perpendicular to the plane of thedrawing. A conduit 25for conveying thermal conditioning fluid isimbedded in the refractory concrete layer 24.

In the construction of the float tank the outer metal shell formed bywalls 22 and 23 defines a mold into which the refractory concrete 24 maybe cast to form the bottom concrete layer after the conduits 25 havebeen positioned in the mold. The basic structure of the furnace wall isthus monolithic and the disadvantages generally arising from thepresence of joints in the furnace walls formed by assembling rows ofprefabricated bricks are avoided. The blocks 26-29 are then positionedon a surface of the layer 24 and are pressed into the surface to causethe cast concrete to enter the dovetail grooves 31. The carbon blocks 30for lining the side walls are then placed in position with their sidefaces 32 resting on the outer blocks of the layer 26. The refractoryconcrete is then cast between the blocks 30 and the side metal wall 23.Some of this concrete will flow into the grooves 31 in the side blocks30. When the concrete sets the blocks lining the bottom and side Therefractory concrete in layer 24 may have a conventional compositionwhich may depend on the various thicknesses of the layers defining afurnace wall and the grain size of its constituents. A composition ofconcrete may comprise 1,320 kilos of chamotte grains of ll mm. having4042 percent of alumina, about 400 kilos of a cement of calciumaluminate and 230 liters of water per cubic meter. Other constituentswhich can be employed for forming a suitable refractory concrete includecorundum, sillimanite and alumina. The proportions of the constituentswill also depend somewhat upon the conditions within the furnace towhich the refractory body will be exposed when in use. The cast concretemass can also be reinforced such as by imbedding netal bars and rods ofvarious configurations therein.

After the concrete has set the tank may be heated sufficiently todegasify the refractory body forming the walls. Degasification preventsthe risk of gaseous components being released into the furnace duringoperation. The refractory bodies which actually form parts of a furnacecan be degasified before the start of the furnace operation. Thedegasification may require a temperature below or above the temperatureto which the bodies will be subjected under normal furnace operatingconditions. A negative pressure can be established within the interiorof the furnace if required to facilitate the degasification.

Refractory bodies to be used in the construction of furnace walls canalso be made in the form of blocks or slabs instead of being cast in theform of monolithic layer. Such blocks or slabs are preferably cast atthe site of construction since they can be then formed to a much largersize than could be conveniently stored and transported to the site. Itis also apparent that the larger the size of the cast slabs the fewerwill be the number of wall joints. By minimizing the number ofjoints inthe floor or wall of a float tank the problem of sealing these jointsagainst penetration by molten material into the furnace wall issubstantially reduced.

A refractory body according to the present invention whether in the formof monolithic slabs or a prefabricated block or brick which istransported to the site has the advantage that the unitary body formedupon the setting of the cast refractory mass possesses the individualproperties attributable to the various materials used in forming therefractory body. The advantages of the present invention will beapparent when considering a refractory body comprising a cast refractorymass having high heat-insulating properties and a surface coating havinga thermal conductivity greater than that of the mass. The greater heatconductivity property imparted to the refractory body by the coatingwill materially effect the conduction of heat only along the coating andconduction of heat through the body in a direction normal to the coatingsurface will have the lower value inherent in the cast refractory mass.This is a contrast to the properties which would be obtained for therefractory body as a whole if the substance used for the coating layerwere distributed throughout the cast mass.

The above described example of a refractory body having a highlyheat-insulating refractory mass and a covering layer of greater thermalconductivity is merely 4 illustrative but refractory bodies havingdifferent thermal conductivities in different directions are ofpractical importance in various furnace tanks. By way of example, in afloat tank used in the manufacture of float glass, it is desired toavoid temperature gradients across transverse zones of the bath ofmolten material since these gradients may cause undesirable variationsin the thickness of the floating glass layer throughout its width.

Constructing the bottom wall of the tank furnace from conventionalrefractory lining blocks may give rise to a problem since these blockshave good heatinsulating properties and as a result there is little heatconduction along the bottom wall. With the present invention, however,the bottom wall can combine a very high resistance to heat transferthrough the thickness of the wall with a significantly lower resistanceto heat transfer along the wall from one part of the tank interior toanother. Such a thermal conductivity differential may also be utilizedin the side walls of the tank.

The material having the higher thermal conductivity may extend over theentire interior surface of the bottom wall or may be limited totransverse zones spaced longitudinally within the tank so that a steepertemperature gradient can be maintained in the longitudinal di rection.Any cast refractory body according to the present invention may beprovided with such a covering layer on each of a plurality of spacedzones.

The present invention may also be utilized to provide refractory liningswith greater resistance to chemical attack. To this end, a coveringlayer of electro-melted refractory material may be applied to a basemass of ordinary and less expensive refractory material.

As disclosed in FIG. 2, the interior surface of the cast refractory masswas covered by a plurality of prefabricated blocks or bricks placed inside-by-side position. If desired, only a part of the refractory masssurface may be covered by such a layer or the layer may comprise asingle prefabricated element in the form of a plate or slab. The layermay also comprise material in discrete form such as granular or fibrousmaterial. The covering layer is bonded to the refractory base mass asthe mass sets. The elements comprising the covering layer may be bondedtogether or the joints could be filled with a bonding agent or mortar. Abonding agent may also be used to secure two or more covering layers inposition. When the covering layer comprises elements of appreciablysmaller size than the refractory mass it is preferable that theseelements have a rectangular, hexagonal or other regular polygonal shapeso that the elements can be accurately positioned in contiguousrelationship to cover a given area. It is preferred that each coveringlayer be composed wholly or partially of carbon. Carbon is preferablesince, unlike refractory concrete, it does not bubble or give offgaseous or vitreous phases. This property is of great importance forthose processes in which the furnace contains a bath of molten materialand the process is liable to being adversely affected by anycontamination of the bath by substances evolving from the wall of thetank. In a float tank, the presence of a carbon layer in contact to thefloat bath is particularly important because the floating glass ribbonwill not adhere to the carbon if the glass ribbon should inadvertentlycome into contact with the wall of the tank.

Another significant advantage of surfacing the refractory body withcarbon results from the reducing properties of carbon. Carbon easilycaptures oxygen and releases it primarily in the form of CO. The actionof carbon is thus beneficial since it is generally necessary to maintaina reducing atmosphere in furnaces in order to avoid the oxidation ofvarious components such as conduits, supporting structures or castingrollers. Where a bath of molten material is employed in the process thisbath should also be protected against oxidation. This is particularlyapplicable to the molten tin bath generally employed in float tanks.Presence of carbon on the interior faces of the walls of the tank thuscontributes significantly to maintaining the quality of the bath.

A further advantage of carbon as a surfacing material is due to its highthermal conductivity. This is of particular importance in a float tankwhere heat exchange along the bottom of the tank assists in providinguniform heat transfer between different regions of the tank.

Such a covering layer for the refractory mass may be composed onlypartially of carbon. A refractory body according to the presentinvention may have at least on one of its surfaces a covering layerformed of members of the same material as the base mass and an adheringcoating of carbon on the material. Substances other than carbon can beused in the same way.

When a covering layer comprises a plurality of separate members it ispreferable that a bonding agent or mortar used in the joints betweenthese members be rich in carbon. The heat conductivity of the coveringlayer is thus improved and if the refractories are in contact withmolten material such as in a float tank penetration of molten materialthrough the'joints of the covering layer is thus prevented. Heattransfer in different directions along the furnace wall may be varied byapplying a conductive bonding agent to certain joints and not to others.

While in most cases one surface of the cast refractory mass will bewholly or partially covered by a layer comprising carbon, it is pointedout that two or more surfaces of the mass can be covered in a similarmanner.

In the covering layer of FIG. 2 comprising blocks 26-30, the bottomsurface of each block was provided with a groove into which some of thecast refractory mass flows when the block is pressed into position on asurface of the mass. This face of a block may be provided with someother form of depression, recess or socket for securing an interlockingrelationship with the cast refractory mass when the latter has set. Thegroove 31 may have a cross section other than trapezoidal, such asrectangular or polygonal and this groove may extend over a portion orthe entire width of the face. Such grooves can be readily formed bymachining the block or during the actual molding of a block depending onits composition. The block may also be provided with a projectingmember, such as a tenon, on its undersurface so that this projectionwill extend into the plastic refractory mass when the block is pressedinto position. This interlocking or interengaging relationship betweenthe blocks comprising the covering layer and refractory mass isparticularly desirable if the covering layer is in contact with a bathof molten material having a higher density than the density of themembers of the covering layer.

The surface of such a covering layer may be machined, particularly wherethis surface is granular or particulate in form, such as when thecovering layer is formed of carbon. This machining removes surfaceroughness and is desirable to prevent the molten material from adheringto the wall and to prevent eddy currents in the bath of molten material.

When a surface wall comprises a plurality of refractory bodies accordingto the present invention it is possible to dispense with any filling inthe joints between the bodies when the abutting faces of these bodiesare accurately formed so that a close fit is possible. However, wherenecessary, these joints can be filled with a cement or the joints may becovered by a refractory material applied on the interior surface of thewall.

Various modifications of the invention as disclosed above are possibleas will be evident upon reference to FIGS. 3-10.

In FIG. 3 the refractory concrete layer 24 is provided with a coveringlayer of carbon blocks 38. Each carbon block 38 is formed with a tenonor tongue projecting, from its undersurface. The tenons of adjacentblocks define grooves or recesses into which the refractory concreteenters when the blocks are pushed into position on the concrete masswhen it is still in the plastic state. Bars 40 are welded at 42 to theinner surface of metal wall 22 to-anchor the refractory mass 24.

In FIG. 4, the covering layer comprises blocks 45 which are similar tothe blocks 38 of FIG. 3 but the tenons have a slightly differentconfiguration. A helical reinforcing bar 46 is imbedded in the concretelayer 24 and is welded at 47 to the inner surface of wall 22.

In FIG. 5, the covering layer comprises blocks 48 having inclined orchamfered edges on their bottom surfaces so that adjacent blocks definea triangular shaped groove to receive the concrete of layer 24.

In FIG. 6 construction, the bottom wall is' lined with blocks 50 eachshaped so that in the bottom thereof there are three longitudinalgrooves 51 which are entered by some of the concrete of the underlyingconcrete layer when the blocks are pushed into position on such layerprior to the setting of the concrete.

In the bottom wall construction of FIG. 7, no outer metal skin or shellis employed. The exterior surface of the bottom wall is thus defined bythe concrete layer 24. The inner surface of the concrete layer is linedwith a covering layer formed of carbon blocks 55 whose lateral sideedgesare stepped. Each lateral face comprises vertical surfaces 56 and58 interconnected by a horizontal surface 57. Blocks of thisconfiguration can be positioned in overlapping relationship asillustrated in FIG. 7. This overlap generally results in joints whichcannot be penetrated by the molten material 33 of the bath. However, ifdesired, the joints between the blocks may be sealed by applyingrefractory cement between the adjoining surfaces 56, 57 and 58 ofsuccessive blocks. The undersurfaces 59 of the blocks are formed with arough or irregular surface in order to secure these blocks to theunderlying refractory concrete layer, 24.

In FIG. 8, a covering layer comprises a plurality of blocks 62 in whoseundersurfaces are formed a plurality of cylindrical bores 63 into whichthe concrete of layer 24 is forced when the blocks 62 are pressed intoposition.

The wall illustrated in FIG. 9 comprises a monolithic refractoryconcrete layer- 24. In the upper surface of the layer 24 there isapplied carbon rubble 65 in particle or granular form. Some of the samerefractory concrete as used in the layer 24 is mixed with the rubble tofunction as a binder. The amount of rubble progressively decreases fromthe outer surface in a direction toward the interior of the layer 24.The binding agent may also have fine carbon particles incorporatedtherein. It is also possible to apply an upper surface layer of finecarbon particles admixed in a binder over the carbon rubble. After theconcrete layer 24 has set, the outer surface of the surface layer may bemachined to remove the roughness and thereby eliminate the possibilityof molten metal clinging to the surface.

The wall construction of FIG. 10 comprises a layer of juxtaposedrefractory concrete members. Each member is prefabricated and comprisesa concrete base slab such as 71, 73, 75 and a surface or covering layerof small juxtaposed carbon blocks 77 positioned on the concrete massbefore it sets. In order to allow for thermal expansion a space 72 maybe formed between adjacent members. The joint may be formed by initiallyfilling the space between the members with a combustible material suchas plywood which will burn away when the furnace tank is operated. It ispreferred to use a plurality-of such separate members in large scalework rather than a single concrete mass extending over the entire wallarea.

It is'pointed out that the present invention not only includes theprocess of forming a refractory body but the refractory bodies ormembers formed by this process. The scope of the invention also includesany furnace wherein at least a part of at least one wall comprises arefractory body according to the present invention with a covering layeror layers on the interior surface of the wall. While the presentinvention is particularly applicable to float furnaces such as used inthe glass making industry it is applicable in the construction of othertypes of furnaces such as fuel-fired or electrically heatedmetallurgical furnaces.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions, andaccordingly, it is desired to comprehend such modifications within thisinvention as may fall within the scope of the appended claims.

What is claimed is:

1. In a method of making a refractory bottom wall or floor of a floatglass furnace, the steps of forming at least a portion of the said floatglass bottom wall by casting a settable refractory concrete mass intothe wall shape, thereafter, while the refractory mass is plastic andbefore it sets putting onto the surface of the plastic refractory mass,a plurality of carbon bricks which bricks consist essentially of carbonparticles, each of the carbon bricks having an interengagingconfiguration defining a recess in the bottom surface of the car bonbricks into which the plastic refractory concrete mass enters bypressing said carbon bricks into the plastic refractory mass so that thebricks are firmly anchored to the refractory mass upon setting of therefractory concrete, the carbon bricks being positioned on the surfaceof the refractory mass in side-by-side relationship to form a floatglass wall surface comprising a minimum number of joints whereby thepenetration of molten material into the wall surface is substantiallyreduced.

2. In a method as claimed in claim 1 wherein the interengagingconfiguration comprises a plurality of cylindrical bores.

3. In a method as claimed in claim 1 wherein the interengagingconfiguration comprises a plurality of bores.

4. In a method as claimed in claim 1 wherein the interengagingconfiguration comprises a plurality of holes.

5. In a method as claimed in claim 1 wherein the interengagingconfiguration comprises a tenon projecting from the bottom surface ofeach bricks, the tenons of adjacent bricks defining grooves therebetweeninto which the refractory concrete enters.

6. In a method as claimed in claim 1 wherein the interengagingconfiguration comprises spaced tenons projecting from the bottom surfaceof each brick to define grooves therebetween into which the refractoryconcrete enters.

7. In a method as claimed in claim 1 whereinthe interengagingconfiguration comprises inclined edges on the bottom surface of eachbrick, adjacent bricks defining triangular-shaped grooves.

8. In a method as claimed in claim 1 wherein the i nterengagingconfiguration comprises a plurality of Iongitudinal grooves in thebottom surface of each brick.

lar surface on the bottom of each brick.

1. In a method of making a refractory bottom wall or floor of a floatglass furnace, the steps of forming at least a portion of the said floatglass bottom wall by casting a settable refractory concrete mass intothe wall shape, thereafter, while the refractory mass is plastic andbefore it sets putting onto the surface of the plastic refractory mass,a plurality of carbon bricks which bricks consist essentially of carbonparticles, each of the carbon bricks having an interengagingconfiguration defining a recess in the bottom surface of the carbonbricks into which the plastic refractory concrete mass enters bypressing said carbon bricks into the plastic refractory mass so that thebricks are firmly anchored to the refractory mass upon setting of therefractory concrete, the carbon bricks being positioned on the surfaceof the refractory mass in side-by-side relationship to form a floatglass wall surface comprising a minimum number of joints whereby thepenetration of molten material into the wall surface is substantiallyreduced.
 2. In a method as claimed in claim 1 wherein the interengagingconfiguration comprises a plurality of cylindrical bores.
 3. In a methodas claimed in claim 1 wherein the interengaging configuration comprisesa plurality of bores.
 4. In a method as claimed in claim 1 wherein theinterengaging configuration comprises a plurality of holes.
 5. In amethod as claimed in claim 1 wherein the interengaging configurationcomprises a tenon projecting from the bottom surface of each bricks, thetenons of adjacent bricks defining grooves therebetween into which therefractory concrete enters.
 6. In a method as claimed in claim 1 whereinthe interengaging configuration comprises spaced tenons projecting fromthe bottom surface of each brick to define grooves therebetween intowhich the refractory concrete enters.
 7. In a method as claimed in claim1 wherein the interengaging configuration comprises inclined edges onthe bottom surface of each brick, adjacent bricks definingtriangular-shaped grooves.
 8. In a method as claimed in claim 1 whereinthe interengaging configuration comprises a plurality of longitudinalgrooves in the bottom surface of each brick.
 9. In a method as claimedin claim 1 wherein the interengaging configuration comprises a rough orirregular surface on the bottom of each brick.